1. Field of the Invention
The present invention relates to a starting device with an air motor for internal combustion engines, and more particularly it relates to a control device for said starting device.
2. Description of the Prior Art
Starting devices with an air motor for internal combustion engines have been known as they are disclosed, for example, in Japanese Patent Publication Nos. 35894/1973 and 21101/1983 and U.S. Pat. No. 4,126,113. Such starting device has a pinion which is mounted on the front end of a driving shaft and adapted to advance while rotating, said pinion meshing with the ring gear of an internal combustion engine to start said internal combustion engine, the operation thereof being such that an air piston fitted to said driving shaft is advanced by a branch flow of compressed air, thereby advancing said driving shaft, and then a large amount of compressed air is fed to an air motor to rotate the latter at high speed, thereby causing the pinion of said driving shaft to start the internal combustion engine.
And the conventional starting device with an air motor uses a solenoid valve as its start command valve and is so arranged that in separating the pinion of said driving shaft from said ring gear after said internal combustion engine has been started, said solenoid valve is used.
In such case, after the starting of the internal combustion engine, if the cut-off operation of the solenoid valve is delayed, said air motor is accelerated to 10 or more times by the rotation of the engine itself at the start, so that in the worst case, it would be damaged.
For this reason, the conventional starting device uses members for a torque limiter or overrun clutch, but these members often get damaged; thus, I have already made a proposal which solves this problem in Japanese Utility Model Application No. 124478/1984. That is, after the internal combustion engine has been started by the air motor, the rotative speed of the ring gear becomes higher than that of the pinion and hence the driving shaft of the pinion is accelerated. Thus, said driving shaft is formed with screw splines and said accelerating force rotates said splines to retract the driving shaft and air piston. As a result, the mechanical valve which actuates the main valve is closed. In this case, the compressed air being fed to the air piston is cut off, so that even if the start command valve is not cut off, there is no danger of the pinion being inadvertently advanced again. This is my proposal.
However, when said conventional technique and such proposal were tested, a new problem arose. That is, the amount of compressed air for advancing the air piston and rotating the air motor gradually at low speed is small, resulting in the lack of air piston pressing force and air motor low-speed rotating force, a fact which is undesirable for the starting device which is expected to meet the need of starting the engine "at one stroke." Thus, it could be thought to increase the diameter of the pipe for feeding compressed air, but an increase in the pipe diameter would result in an increase in rigidity, making piping operation more difficult, requiring more space for installation and adding to weight.